In medical practice, identification of epidural space is required for therapeutic, anaesthetic and diagnostic procedures.
The currently used techniques rely on high level of manual skill and dexterity and require specialised training. These techniques are not uncommonly associated with technical difficulties or complications.
In the conventional method; anaesthetist uses his/her skill in locating the epidural space by injecting the air or saline into the epidural space. The anesthetist ensures that the patient stays in the proper position while locating the space. In the spinal column, once the tip of the epidural needle just enters the deeper part of interspinous ligament, the needle is held in place. A saline or air filled syringe is attached tightly to the hub of the needle. The epidural needle is advanced holding its shaft or wings mounted on the hub of the needle. A constant pressure is built up in the syringe by manual compression of piston. Once the tip of the epidural needle enters the epidural space, the anesthetist feels sudden loss of friction enabling him to inject the pressurised saline to confirm the position in the epidural space. This method is depicted through the FIG. 1.
The main disadvantage of this procedure is, it takes longer to establish the space and technically more demanding.
To overcome this disadvantage there are several methods or devices that have been invented and adopted. While so, each inventor claims his device and method having simpler technology, user friendly and most advanced.
U.S. Pat. No. 7,175,608 (Maan Hasan et al.,) teaches the working and construction of a device for locating the epidural space. The device includes a diaphragm that is adapted for pressurization. The diaphragm bulges outwards when the device is pressurized. Also, the device is adapted to connect a needle. In some embodiments the device is pressurized with air or saline. In some other embodiments the device includes an injection port for injection of pressurized fluid. This device is depicted in FIG. 2 hereof.
U.S. Pat. No. 6,773,417 (James F. Fitzgibbons et al.,) teaches the working and construction of the device for locating the epidural space. The epidural space locating device comprises a first end and a second end and a longitudinal passage way extending there through, the first end of which is coupleable to a luer assembly; and a collapsible bellows camber having one end coupled to the other end of the body section and other end exposed so as to permit pressure to be exerted thereon by one or more digits of a hand, wherein positive pressure within the bellows chamber maintains the integrity of the shape of the bellows chamber and wherein negative or zero pressure within the bellows chamber facilitates the collapsing of the shape of the bellows chamber thus indicating the locating of the epidural space by a needle that is coupled to the luer assembly; wherein the loss of pressure within the bellows chamber is sensed by the one or more digits of the hand as the shape of the bellows chamber collapses. This device is depicted in FIG. 3 hereof.
U.S. Pat. No. 5,902,273 (Ian Y Yang et al.,) teaches the working and construction of the device for locating the epidural space. According thereto, a syringe that can be positively pressurized via a one-way valve and illustrated by a pressure indicator is designed to be used with an epidural needle to identify epidural space and to protect the dura being punctured when a loss of positive pressure occurs. The inventive syringe housing having a plunger with a longitudinal bore for pressurization is connected to a pressure chamber via the one-way valve allowing air flow only into the pressurization chamber from the syringe housing. A needle is air-tightly connected to the pressurization chamber with a needle connecting device. A pressure indicator connected to the pressurization chamber objectively indicates the loss of positive pressure when the needle enters the epidural space. The positively pressurized air from the needle deflects the dura away from the needle tip’ and prevents dural puncture. This device is depicted in FIG. 4 hereof.
U.S. Pat. No. 4,919,653 (Antonio E. Martinez et al) teaches the working and construction of device for locating the epidural space: According thereto, the device consists of a cannula constituted of a supporting body and a pipe. There exists a magnet surrounding a sleeve in the axial direction and positioned at the back part of the supporting body in the supporting body. When a catheter is inserted into the back of a patient and reaches the epidural cavity, its vacuum condition is sensed by means of a pressure sensor and the magnet and an alarm are actuated. This device is depicted in FIG. 5 hereof.
U.S. Pat. No. 4,175,567 (Bhupendra C, Patel) teaches the working and construction of the device for locating the epidural space. According thereto is method of locating the epidural space in a patient's body with a needle assembly having a flexible film defining a closed cavity which communicates with a needle of the assembly, comprising the steps of positioning a tip of the assembly adjacent the epidural space, and advancing the assembly into the body while determining whether the film flexes inwardly or outwardly relative to the assembly to ascertain the position of the needle assembly tip in the patient's body. This device is depicted in FIG. 6 hereof.
W005004947 (Bryan Vincent E. et al.,) teaches the working and construction of device for locating the epidural space. According thereto, a system for grasping, holding, stabilizing, and selectively releasing tissue with minimal damage to the tissue is disclosed. The system can further include a device that signals entry into the epidural space. A tubular member is provided having at a distal tip an annular surface surrounding a terminal port and at least one barb projecting at an angle from the annular surface for grasping and controlling the tissue. Each barb is formed having a sharp edge configured to grasp the tissue as the tubular member is rotated about its longitudinal axis. One implementation of the system includes a plurality of unidirectional barbs spaced around the annular surface. The system can further include an indicator mechanism that gives a visual and a tactile indication of when the tubular member, such as a cannula, encounters and penetrates tissue. The system facilitates the appropriate placement of a n epidural or subdural catheter or patch of any kind. This device is depicted in FIG. 7 hereof.
MX9603835 (Federick C. Houghton) teaches the working and construction of device for locating the epidural space. According thereto, a regulating device for variably regulating the length of a combined spinal epidural needle and the method of practising the same is disclosed. In one variant, the regulating device features a pair of substantially concentricity disposed sliding members to which each of the epidural needle and spinal needle may be separately fitted. A spring element is provided to selectably engage the spinal needle. The spring element includes one end fixed to the sliding member securing the epidural needle, a free end manipulable by a user, and at least one passage or opening disposed between the fixed and free ends through which the spinal needle passes. The opening is configured to permit either gripping or free sliding of the spinal needle depending on the practitioner's actuation of the spring element. By actuation of the spring element, the practitioner may control axial movement between the sliding members, thereby regulating the extension of the spinal needle relative to the epidural needle. The sliding members may be configured in a variety of shapes or dimensions to accommodate various combinations of spinal and epidural needles. The device may be provided pre-assembled with either one or both of the spinal needle or epidural needle, or it may be employed with a spinal needle, epidural needle, or both separately sourced. This device is depicted in FIG. 8 hereof.
U.S. Pat. No. 5,205,828 (Kedem Dan) teaches the working and construction of device for locating the epidural space. According thereto, the stilette is connected at its posterior end to a displaceable piston located in the syringe. The piston, which is constrained to move between two fixed points of pre-selected separation, is immobilized in its posterior position by a latch. Means are provided for biasing the piston anteriorly.
In another embodiment thereof, the device is accomplished by connecting the anterior piston to a biasing piston by a spring. The biasing piston can be set in one of two positions. The posterior position does not compress the spring. The anterior positions tenses the spring, anteriorly biasing the displaceable piston. In another, and preferred, embodiment of the present invention, a stilette is not used at all. Rather, the needle comes equipped with a catheter, preferably a blind end catheter, which runs from the tip of the needle, through both the displaceable and biasing pistons and out the posterior end of the syringe. The needle is inserted as before. However, when the epidural space is reached, the displaceable piston jumps forward, passing the anterior tip of the catheter into the epidural space tissue and thereby exposing the openings near the tip of the catheter and making them immediately available for the injection of anesthetizing fluids. This device is depicted in FIG. 9 hereof.
GB2226496 (Ziko Abdul Rahman Osman) teaches the working and construction of device for locating the epidural space. According thereto, the device comprises a rotor-containing chamber fitted on to the end of a syringe vessel and with the syringe needle projecting from the end of the chamber and in fluid-flow communication via the chamber with the syringe vessel. The negative pressure experienced at the tip of the needle as it enters the epidural space of a patient, in use, is transmitted via the needle to the chamber and causes the rotor to rotate. The rotation is visible through the transparent walls of the chamber and as soon as it is seen it tells the practitioner that he has found the epidural space. The device, consisting of rotor-containing chamber with needle projecting from one end thereof, and with the other end of the device fitting on to the syringe vessel in use, may be manufactured as a self-contained unit; or it may form an inherent extension of the syringe vessel and be constructed as part of the syringe from the outset. This device is depicted in FIG. 10 hereof.
ES 8706023 (Yuste Pascual Jose) teaches the working and construction of device for locating the epidural space. According thereto, an apparatus for the location of epidural, peridural or extradural spaces, which includes a needle or trocar for the injection of an isotonic saline solution by means of an infusion pump capable of providing a continuous flow, in such a manner that the various pressures produced when passing through the different anatomical structures are monitored until a sudden drop occurs which makes it possible to ascertain that the epidural space has been reached. Application The location of the epidural space, for the administration of chemical/pharmaceutical products, for diagnosis (diagnostics), and for analgesic or anaesthetic purposes. This device is depicted in FIG. 11 hereof.
In any of the above inventions disclosed, the stopping of further advancement of the needle is not addressed. Once after the reaching the epidural space, further forward movement of the hand has to be manually stopped. This is a safety concern as any slight inertial advancement of the hand may make the needle to move further, possibly causing dural puncture.